The present invention relates to a magnetic composition and more specifically to a method for producing a polymeric resin bonded magnetic composition and magnetic composites comprising such a composition.
In recent years, in accordance with the diversification and microminiaturization of electronic devices, parts and the like, magnetic moldings with complicated forms or microstructures have been required in various technical fields. Generally, magnetic moldings are produced by pressing magnetic powder such as ferrite powder and then sintering the pressed magnetic powder at a temperature of at least 1000° C. However, the moldings are often contracted when the pressed magnetic powder is sintered, and the production cost is high since the yield is markedly lowered when producing moldings that have complicated forms or microstructures. Further, such magnetic moldings are difficult to process mechanically, and the obtained magnetic moldings are brittle and easily chipped. Therefore, the development of a complicated and microstructural shapes is required to solve these problems for applications in various technical fields.
A known polymeric resin-bonded magnetic composition used as a magnetic core for a transformer and the like is produced by mixing iron powder or ferrite powder with polymeric resin Components such as polyphenylene sulfide, polyalkylene terephthalate, polyetifylene, polypropylene, polybutene, polyvinyl chloride, or acrylonitrile-butadiene-styrene resin. The methods described in U.S. Pat. No. 6,338,900 provide a means of obtaining an injection moldable magnetic composite but the initial magnetic permeability is less than 30 due to low loading of magnetic material, which low loading is necessary to make the composite moldable. Therefore, there exists a need to develop a polymeric resin bonded magnetic composite that exhibits permeability characteristics that are required by the electrical and electronic industries. Typical uses of such magnetic composites lie in the areas of filters for power supplies, choke coils for video systems, motors and stators, transformer cores and the like.